The Biogeology of a Population of Prairie Rattlesnakes (Crotalus viridis) at a High Elevation Site i

Boback, Scott M.

bobacks@dickinson.edu

Department of Biology

Dickinson College

Carlisle, Pennsylvania, USA

Edwards, Ben

Hayes, Jorden

Department of Earth Sciences

Dickinson College

Carlisle, Pennsylvania, USA

During seasonal weather extremes, many temperate animals enhance survival by seeking out temporary or semi-permanent shelters/refugia during weather extremes. Such places may have greater significance for animals living at high elevations and/or latitudinal extremes. We studied a population of the Prairie Rattlesnake (Crotalus viridis) using a high elevation (2225 m) hibernaculum/den in northwestern Colorado and document the geology and overwintering biology of this population. Remote cameras, with thermistors, were positioned at den entrances to document the timing of ingress and egress as well as basking activities around the den. Maternal rookeries were documented and monitored for parturition. We also employed radio-telemetry and drone photogrammetry to characterize seasonal dispersal to and from the den and to generate a digital elevation model of the study site. Lastly, we initiated work aimed at mapping the subterranean geometry of the den using ground-penetration radar (GPR). A digital elevation model produced from drone photogrammetry and GPR data indicate the den is poised within an igneous sill or dike with some significant subterranean structural features. Our preliminary data demonstrate this population of C. viridis exhibits a short active season with egress in late May/early June and ingress from late August through October. Females begin parturition in late August and continue into September. Non-gravid females and males disperse moderate distances (> 3 km) during spring egress. The significance of these results within the context of den permanence/predictability and global temperature increases will be discussed.